Imaging apparatus having plurality of operating states

ABSTRACT

There is described an imaging apparatus having an image sensor, and a plurality of operating states. Operation of the imaging apparatus can be differentiated between the operating states. In one operating state, the imaging apparatus can capture a frame of image data having image data corresponding to a predetermined number of pixels of the image sensor. The operating states of the imaging apparatus can be user selectable.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/895,803, filed Aug. 27, 2007, (U.S. Patent ApplicationPublication No. 2008/0170275, entitled, “Bar Code Reading Device HavingPlurality of Operating States” which is incorporated herein by referencein its entirety, which a divisional application of U.S. patentapplication Ser. No. 09/766,922, filed Jan. 22, 2001, (U.S. Pat. No.7,268,924) entitled, “Optical Reader Having Reduced ParameterDetermination Delay” which is incorporated herein by reference in itsentirety. In addition, the present application incorporates by referencein its entirety U.S. patent application Ser. No. 09/766,806 (now U.S.Pat. No. 6,637,658 B2) filed Jan. 22, 2001 entitled, “Optical ReaderHaving Partial Frame Operating Mode,” which application is incorporatedby reference in the aforementioned U.S. patent application Ser. No.09/766,922 filed Jan. 22, 2001. This application is also related to U.S.patent application Ser. No. 11/238,176, filed Sep. 28, 2005, (U.S. Pat.No. 7,428,079) entitled “Bar code reading device having partial frameimage capture operating mode,” U.S. patent application Ser. No.10/651,298, filed Aug. 28, 2003, (U.S. Pat. No. 7,270,273) entitled“Optical Reader Having Partial Frame Operating Mode,” and U.S. patentapplication Ser. No. 11/637,231, filed Dec. 11, 2006 (U.S. Pat. No.7,434,733) entitled “Optical Reader Having Partial Frame OperatingMode,” and U.S. patent application Ser. No. 12/249,742, filed Oct. 10,2008 entitled “Reading Apparatus Having Partial Frame Operating Mode.”

FIELD OF THE INVENTION

The present invention relates to a bar code reading device generally andparticularly to a bar code reading device having a plurality ofoperating states.

BACKGROUND OF THE PRIOR ART

Prior to commencing comprehensive image data processing, which mayinclude e.g., searching for symbol or character representations,decoding and character recognition processing, presently availableoptical readers clock out and capture in a memory location at least oneexposure test frame of image data, read pixel data from thememory-stored exposure test frame to determine an exposure parametervalue that is based on actual illumination conditions, then utilize theexposure parameter value in the exposure of a frame of image data thatis clocked out, and then subjected to searching, decoding, and/orcharacter recognition processing. The frame of image data exposedutilizing the exposure parameter based on actual illumination conditionsis not available for reading until after it is clocked out. Presentlyavailable optical readers therefore exhibit an appreciable inherentexposure parameter determination delay. Readers having higher resolutionimagers have slower frame clock out rates and therefore longer exposureparameter determination delays.

There is a growing demand for higher resolution optical readers,including optical readers that incorporate mega pixel image sensors.Accordingly, there is growing need to address the parameterdetermination delay problem associated with presently available opticalreaders.

Optical readers having 2D image sensors commonly are used to read both1D and 2D symbols. Some optical readers having a 2D image sensor read a1D symbol by capturing a 2D image representation, or “frame” of imagedata corresponding to a target area which comprises a 1D symbol, andlaunching a scan line or lines in order to attempt to decode for 1Dsymbols which may be represented in the area. Other optical readershaving 2D image sensors read 1D symbols by capturing a 2D imagerepresentation of an area containing the 1D symbol, preliminarilyanalyzing the image data represented in the area to determine that theimage data comprises a representation of a 1D symbol, and then launchinga scan line in an attempt to decode for the 1D symbol determined to bepresent. In either case, a full frame 2D image representation iscaptured in order to decode for a 1D symbol.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1 b are image maps illustrating possible low resolutionframes of image data clock out during a low resolution frame clock outmode of the invention;

FIG. 2 a is a block diagram of an optical reader of a type in which theinvention may be incorporated;

FIGS. 2 b-2 h show various types of optical reader housings in which theinvention may be incorporated;

FIG. 3 a is a process flow diagram illustrating frame clockingoperations in an optical reader having an image sensor including aone-frame buffer;

FIG. 3 b is a time line illustrating frame clock out operations in aprior art optical reader;

FIG. 3 c is a time line illustrating a frame clock out of operations inan optical reader operated according to the invention.

[Beginning of section excerpted from U.S. patent application Ser. No.09/766,806].

FIGS. 4 a-4 g illustrate various image data patterns that may becaptured by an optical reader operating in a partial frame capture modeaccording to the invention;

FIG. 5 a is a block diagram of an optical reader of a type in which theinvention may be incorporated;

FIGS. 5 b-5 h show various types of optical reader housings in which theinvention may be incorporated.

[End of section excerpted from U.S. patent application Ser. No.09/766,806].

SUMMARY OF THE INVENTION

There is described an imaging apparatus having an image sensor, and aplurality of operating states. Operation of the imaging apparatus can bedifferentiated between the operating states. In one operating state, theimaging apparatus can capture a frame of image data having image datacorresponding to a predetermined number of pixels of the image sensor.The operating states of the imaging apparatus can be user selectable.

DETAILED DESCRIPTION OF THE INVENTION

When operated to generate valid pixel data, presently available opticalreading devices clock out electrical signals corresponding to pixelpositions of an image sensor at a uniform clock out rate such that theelectrical signal corresponding to each pixel of the image sensor arrayaccurately represents light incident on the pixel.

By contrast, an image sensor of the present invention is made to operateunder two major frame capture modes, a “low resolution” frame clock outmode and a “normal resolution” frame clock out mode. In a “lowresolution” mode of operation, an image sensor according to theinvention is operated to clock out electrical signals corresponding tosome pixels of an image sensor array at a high clock out rate and otherpixels of the image sensor at a normal clock out rate. Clocking out aportion of the electrical signals using a faster than normal clock outrate results in a reduction in the overall frame clock out time whileclocking out a portion of the signals at a normal clock out rate enablesthe generation of pixel data sufficient to enable determination ofparameter settings for use in subsequent frame captures. In a “normalresolution” mode of operation the image sensor is operated to clock outelectrical signals corresponding to pixels of the array using a singleuniform clock out speed as in prior art readers. The low resolution modeof operation may also be carried out by clocking out electrical signalscorresponding to only a portion of a frame's pixels and not clocking outelectrical signals corresponding to the remaining pixels.

A reader configured in accordance with the invention clocks out andcaptures in a memory storage location at least one parameterdetermination frame of image data in a “low resolution” frame capturemode, reads pixels of the parameter determination frame in establishingat least one operation parameter that is based on actual illuminationconditions, utilizes the determined operation parameter in clocking outa subsequent frame of image data in a “normal resolution mode,” thencaptures and subjects the frame of image data clocked out utilizing theoperation parameter to image data searching, decoding, and/orrecognition processing. The reader may be adapted to decode a decodablesymbol represented in a frame of image data developed utilizing adetermined operating parameter.

An optical reading system is which the invention may be employed isdescribed with reference to the block diagram of FIG. 2 a.

Optical reader 10 includes an illumination assembly 20 for illuminatinga target object T, such as a 1D or 2D bar code symbol, and an imagingassembly 30 for receiving an image of object T and generating anelectrical output signal indicative of the data optically encodedtherein. Illumination assembly 20 may, for example, include anillumination source assembly 22, together with an illuminating opticsassembly 24, such as one or more lenses, diffusers, wedges, reflectorsor a combination of such elements, for directing light from light source22 in the direction of a target object T. Illumination assembly 20 maycomprise, for example, laser or light emitting diodes (LEDs) such aswhite LEDs or red LEDs. Illumination assembly 20 may include targetillumination and optics for projecting an aiming pattern 27 on target T.Illumination assembly 20 may be eliminated if ambient light levels arecertain to be high enough to allow high quality images of object T to betaken. Imaging assembly 30 may include an image sensor 32, such as a 1Dor 2D CCD, CMOS, NMOS, PMOS, CID OR CMD solid state image sensor,together with an imaging optics assembly 34 for receiving and focusingan image of object T onto image sensor 32. The array-based imagingassembly shown in FIG. 2 a may be replaced by a laser array basedimaging assembly comprising multiple laser sources, a scanningmechanism, emit and receive optics, at least one photodetector andaccompanying signal processing circuitry.

Optical reader 10 of FIG. 2 a also includes programmable control circuit40 which preferably comprises an integrated circuit microprocessor 42and an application specific integrated circuit (ASIC 44). The functionof ASIC 44 could also be provided by field programmable gate array(FPGA). Processor 42 and ASIC 44 are both programmable control deviceswhich are able to receive, output and process data in accordance with astored program stored in memory unit 45 which may comprise such memoryelements as a read/write random access memory or RAM 46 and an erasableread only memory or EROM 47. RAM 46 typically includes at least onevolatile memory device but may include one or more long termnon-volatile memory devices. Processor 42 and ASIC 44 are also bothconnected to a common bus 48 through which program data and workingdata, including address data, may be received and transmitted in eitherdirection to any circuitry that is also connected thereto. Processor 42and ASIC 44 differ from one another, however, in how they are made andhow they are used.

More particularly, processor 42 is preferably a general purpose,off-the-shelf VLSI integrated circuit microprocessor which has overallcontrol of the circuitry of FIG. 2 a, but which devotes most of its timeto decoding image data stored in RAM 46 in accordance with program datastored in EROM 47. Processor 44, on the other hand, is preferably aspecial purpose VLSI integrated circuit, such as a programmable logic orgate array, which is programmed to devote its time to functions otherthan decoding image data, and thereby relieve processor 42 from theburden of performing these functions.

The actual division of labor between processors 42 and 44 will naturallydepend on the type of off-the-shelf microprocessors that are available,the type of image sensor which is used, the rate at which image data isoutput by imaging assembly 30, etc. There is nothing in principle,however, that requires that any particular division of labor be madebetween processors 42 and 44, or even that such a division be made atall. This is because special purpose processor 44 may be eliminatedentirely if general purpose processor 42 is fast enough and powerfulenough to perform all of the functions contemplated by the presentinvention. It will, therefore, be understood that neither the number ofprocessors used, nor the division of labor there between, is of anyfundamental significance for purposes of the present invention.

With processor architectures of the type shown in FIG. 2 a, a typicaldivision of labor between processors 42 and 44 will be as follows.Processor 42 is preferably devoted primarily to such tasks as decodingimage data, once such data has been stored in RAM 46, recognizingcharacters represented in stored image data according to an opticalcharacter recognition (OCR) scheme, handling menuing options andreprogramming functions, processing commands and data received fromcontrol/data input unit 39 which may comprise such elements as trigger74 and keyboard 78 and providing overall system level coordination.

Processor 44 is preferably devoted primarily to controlling the imageacquisition process, the A/D conversion process and the storage of imagedata, including the ability to access memories 46 and 47 via a DMAchannel. Processor 44 may also perform many timing and communicationoperations. Processor 44 may, for example, control the illumination ofLEDs 22, the timing of image sensor 32 and an analog-to-digital (A/D)converter 36, the transmission and reception of data to and from aprocessor external to reader 10, through an RS-232, a network such as anEthernet, a serial bus such as USB, a wireless communication link (orother) compatible I/O interface 37. Processor 44 may also control theoutputting of user perceptible data via an output device 38, such as abeeper, a good read LED and/or a display monitor which may be providedby a liquid crystal display such as display 82. Control of output,display and I/O functions may also be shared between processors 42 and44, as suggested by bus driver I/O and output/display devices 37′ and38′ or may be duplicated, as suggested by microprocessor serial I/Oports 42A and 42B and I/O and display devices 37″ and 38′. As explainedearlier, the specifics of this division of labor is of no significanceto the present invention.

FIGS. 2 b through 2 g show examples of types of housings in which thepresent invention may be incorporated. FIGS. 2 b-2 g show 1D/2D opticalreaders 10-1, 10-2 and 10-3. Housing 12 of each of the optical readers10-1 through 10-3 is adapted to be graspable by a human hand and hasincorporated therein at least one trigger switch 74 for activating imagecapture and decoding and/or image capture and character recognitionoperations. Readers 10-1 and 10-2 include hard-wired communication links79 for communication with external devices such as other data collectiondevices or a host processor, while reader 10-3 includes an antenna 80for providing wireless communication device or a host processor.

In addition to the above elements, readers 10-2 and 10-3 each include adisplay 82 for displaying information to a user and a keyboard 78 forenabling a user to input commands and data into the reader.

Any one of the readers described with reference to FIGS. 2 b through 2 gmay be mounted in a stationary position as is illustrated in FIG. 2 hshowing a generic optical reader 10 docked in a scan stand 90. Scanstand 90 adapts portable optical reader 10 for presentation modescanning. In a presentation mode, reader 10 is held in a stationaryposition and an indicia bearing article is moved across the field ofview of reader 10.

As will become clear from the ensuing description, the invention neednot be incorporated in a portable optical reader. The invention may alsobe incorporated, for example, in association with a control circuit forcontrolling a non-portable fixed mount imaging assembly that capturesimage data representing image information formed on articles transportedby an assembly line, or manually transported across a checkout counterat a retail point of sale location. Further, in portable embodiments ofthe invention, the reader need not be hand held. The reader may be partor wholly hand worn, finger worn, waist worn or head worn for example.

Referring again to particular aspects of the invention, a low resolutionframe clock out mode of the invention is described in detail withreference to the pixel maps of FIGS. 1 a and 1 b. Control circuit 40establishes a clock out rate for clocking out an electrical signalcorresponding to a pixel of an image sensor 32 by appropriate statecontrol of control signals in communication with image sensor 32. In thepresent invention, image sensor 32 is selected to be of a type whosepixel clock out rate can be varied by way of control signals receivedfrom control circuit 40. In presently available optical readers, animage sensor's pixel clock out rate is not changed during the course ofclocking out of a frame of image data.

In a “low resolution” frame clock out mode of the invention, however,control circuit 40 causes image sensor 32 to clock out electricalsignals corresponding to the pixels of the array at least two speedsduring a single frame capture period. During a single frame clock outperiod, control circuit 40 controls image sensor 32 so that some pixelsare clocked out at normal clock out rate sufficient to developelectrical signals accurately representing the intensity of light at therespective pixel positions, while other pixels are either not clockedout or are clocked out at a clock out rate which may be insufficient toallow development of electrical signals that accurately represent theintensity of light at the respective pixels but which neverthelessresults in a reduction of the overall frame clock out time of the frameof image data being clocked out.

FIG. 1 a shows a schematic diagram of an exemplary image map frame thatis clocked out according to the low resolution frame clock out mode ofthe invention and then captured into memory 45. The image map is dividedinto “zones” of valid data and invalid data. Valid zones 84 shown arerows of pixels that are clocked out at a normal clock out speed whileinvalid zones 86 shown are rows of pixels that are clocked out at afaster clock out speed, which is normally (but not necessarily) a speedinsufficient to allow development of electrical signals accuratelyrepresenting the intensity of light at a pixel.

FIG. 1 b shows another possible division of an image map into validzones and invalid zones. This type of embodiment in which valid zones 84comprise less than full pixel rows is conveniently realized byappropriate control of an image sensor manufactured using CMOSfabrication methods. Using CMOS fabrication methods, an image sensor canbe merged with a microprocessor, an ASIC, or another timing device on asingle die to the end that a pre-established clocking sequence in whicha pixel clock out rate is changed multiple times during the course ofclock out a frame of image data may be actuated in response to theactivation of a single control signal in communication with image sensor32.

Using CMOS fabrication techniques, image sensors are readily made sothat electrical signals corresponding to certain pixels of a sensor canbe selectively clocked out without clocking out electrical signalscorresponding to remaining pixels of the sensor. CMOS image sensors areavailable from such manufacturers as Symagery, Pixel Cam, Omni Vision,Sharp, Natural Semiconductor, Toshiba, Hewlett-Packard and Mitsubishi.Further aspects of a partial frame clock out mode are described incommonly assigned application Ser. No. 09/766,806 entitled “OpticalReader Having Partial Frame Operating Mode,” now U.S. Pat. No. 6,637,658filed concurrently herewith and incorporated herein by reference.

The invention is also conveniently realized with use of an image sensorhaving an image sensor discharge function. Image sensors having adischarge function are typically adapted to receive a discharge clockout signal which when active results in all pixels of a frame being readout at a high clock out rate insufficient to allow development ofelectrical signals. In presently available readers having a directionalfunction, a control circuit sets the discharge clocking signal to anactive state while clocking out an initial “discharge period” frame ofimage data immediately after reception of a trigger actuation. Thisinitial discharge process removes any residual charges built up on imagesensor 32 prior to capturing a first frame including valid pixel data.

For producing an image map divided into valid and invalid zones using animage sensor having a discharge function, control circuit 40 may be madeto intermittently change the state of a discharge clock out signalduring a frame clock out period during which image sensor 32 isotherwise operated according to a normal resolution clock out mode.

An exemplary embodiment of the invention in which the invention isemployed in a reader equipped with a SONY ICXO84AL CCD image sensor(that includes a one frame analog buffer memory) and a SONY CXD2434TQtiming generator is described with reference to FIGS. 3 a, 3 b and 3 c.FIG. 3 a shows a flow diagram, of an imaging system in which the imagesensor includes a one frame buffer memory. For purposes of illustratingthe advantages of the invention, FIG. 3 b shows a time line illustratingthe time required to clock out and capture a frame of image data usefulfor searching and decoding in a prior art reader having a buffer memorynot configured to operate in accordance with a low resolution frameclock out mode. FIG. 3 c shows a time line illustrating the timerequired to clock out and capture a frame of image data useful forsearching, decoding, and recognizing characters in a reader having abuffer memory configured to operate in a low resolution frame clock outmode according to the invention.

When a reader includes a one frame buffer memory, then the activation ofan appropriate frame clock out signal by image sensor 32 causeselectrical charges representative of light on pixels of an imagesensor's pixel array 32 a to be transferred to analog buffer memory 32 band causes electrical signals corresponding to pixel value storagelocations of buffer 32 b (representing light on the pixels during aprevious timing period) to be clocked out to analog to digital converter36 so that the frame of image data stored on buffer memory can becaptured in memory 45, wherein the data may be read by control circuit40.

Referring to time line 92 corresponding a prior art reader it can beseen that a substantial parameter determination delay is present withoutuse of a low resolution frame capture mode according to the invention.At time T0, control circuit 40 activates a frame discharge controlsignal so that residual charges built up in the storage locations ofbuffer memory 32 b are eliminated or “cleaned” during clock out periodCP0.

At time T1, control circuit 40 activates a frame clocking signal tocommence the clock out a first frame of pixel data according to a normalresolution frame clock out mode (the pixel data clocked out during clockout period CP1 is normally invalid pixel data). During clock out periodCP1, the charges built up on pixel array 32 a during clock out periodCP0 are transferred to buffer memory 32 b and then clocked out to A/Dconverter 36. Also during clock out period CP1 pixel array 32 a isexposed to light for a time determined by an exposure parameter value,e₀, that was previously transmitted at time Te₀ prior to time T1. Theexposure parameter e₀ is based on previous exposure values during aprevious trigger actuation period or based on expected illuminationconditions, but is not based on actual illumination conditions present.

At time T2, control circuit 40 activates a frame clock out signal tocommence the clock out of a second frame of image data in accordancewith a normal resolution frame clock out mode. During clock out periodCP2, the charges built up on pixel array 32 a during clock out periodCP1 are transferred to buffer memory 32 b and then clocked out to A/Dconverter 36. Also during clock out period CP2 pixel array 32 is exposedto light for a time determined by an exposure parameter value, e₁, thatwas previously transmitted at time Tel prior to time T2. The exposureparameter e₁, like exposure parameter e₀, also cannot be based on actualillumination conditions since the most recent frame image data availablefor reading by circuit 40 prior to the transmittal of exposure parametere₁ is the invalid frame data resulting from transmittal of framedischarge signal at time T0.

At time T3, control circuit 40 activates a frame clock out signal tocommence the capture of a third frame of image data in accordance with anormal resolution frame clock out mode. During clock out period CP3, thecharges built up on pixel array 32 a during clock out period CP2 aretransferred to buffer memory 32 b and then clocked out to A/D converter36. Also during clock out period CP3, pixel array 32 a is exposed tolight for a time determined by an exposure parameter value, e₂, that waspreviously transmitted at time Te₂ prior to time T3. Unlike the previousexposure values e₀ and e₁, the exposure parameter value e₂ can be avalue determined from actual illumination conditions since the frame ofimage data resulting from pixel array 32 a being exposed to light duringclock out period CP1, is available for reading by control circuit 40prior to the time that the exposure parameter e₂ must be communicated toimage sensor 32. However, because of the built in one frame delayresulting from the presence of buffer 32 b, it is seen that a frame ofimage data clocked out while being exposed with the exposure parametervalue e₂, determined based on actual illumination conditions, will notbe available for reading by control circuit unit after the expiration ofclocking period CP4. Accordingly, it can be seen that the above readerexhibits a typical parameter determination delay of four normalresolution clock out periods, CP1+CP2+CP3+CP4 plus the frame dischargeclock out parameter CP0. The normal resolution frame clock out period ofthe above-referenced SONY image sensor is about 33.37 ms and the framedischarge period is about 8.33 ms, resulting in a typical-case totalparameter determination delay in the example described of 140 ms (anearlier frame may be subjected to image data searching, decoding, andrecognition if e₀ or e₁ yields an image of acceptable quality).

Advantages of operating image sensor 32 according to a low resolutionframe clock out mode of operation are easily observable with referenceto time line 94 corresponding to a reader having an image sensoroperated in accordance with a low resolution frame clock out mode. Inthe example illustrated by time line 94 control circuit 40 operatesimage sensor as described in connection with FIG. 3 b except thatcontrol circuit 40 operates image sensor 32 according to a lowresolution frame clock out mode during clocking periods CP1, CP2, andCP3. Because electrical signals corresponding to only some of the pixelsduring these timing periods are clocked out at speeds sufficiently slowto read valid image data, the total frame clock out time associated withthese clocking periods is significantly shorter than that of a frameclocked out according to a normal resolution frame clock out mode. In anexemplary embodiment in which control circuit 40 alternatingly changesthe state of a discharge clock out control signal (known as an EFSsignal) in communication with a SONY ICXO84AL CCD image sensor, toresult in a zone division pattern having valid zones comprising fourpixel rows clocked out at normal speed bounded by invalid rows havingeighteen rows of pixels clocked out at high speed, the low resolutionframe clock out rate is 8.52 ms. The overall typical parameterdetermination delay is therefore reduced to T0+T1+T2+T3+T4=66.2 ms ascompared to the 140 ms delay in the prior art reader example describedwith reference to FIG. 3 a.

In the example described in which image sensor 32 comprises a one framebuffer 32 b, pixel array 32 a is exposed to light for at least some timecurrently as electrical signals are clocked out from buffer 32 b. In thecontrol of presently available image sensors that do not have one framebuffers, frame clock out periods normally follow frame exposure periodswithout overlapping the exposure periods.

A low resolution parameter determination frame of image data clocked outusing a low resolution clock out mode is useful for determining anexposure control parameter because exposure parameter values can beaccurately determined by sampling only a small percentage of pixelvalues from a frame of image data. In fact, for improving the processingspeed of an optical reader it is preferred to determine an exposurecontrol value based on a sampling of a small percentage of pixel valuesfrom a frame of image data. The proper exposure parameter setting variessubstantially linearly with illumination conditions, and therefore isreadily determined based on a sampling of pixel values from a singleframe of image data.

Additional reader operating parameters can be determined by readingpixel values from a frame of image data clocked out according to a lowresolution clock out mode of the invention. These additional parameterswhich may be determined from a low resolution parameter determiningframe of image data include an amplification parameter for adjusting thegain of an amplifier prior to analog-to-digital conversion, anillumination level parameter for adjusting the current level deliveredto, and therefore the radiance of light emitted from LEDs 22, anillumination time parameter for adjusting the on-time of LEDs 22, alight level parameter for adjusting a light level of a subsequentlycaptured frame of image data, a dark level parameter for adjusting adark level of a subsequently captured frame of image data, and ananalog-to-digital converter reference parameter for adjusting areference voltage of analog-to-digital converter 36.

Referring to FIGS. 4 a-4 g the invention is an optical reader equippedwith a 2D image sensor that is configured to operate in a partial framecapture mode. In a partial frame clock out mode, a control circuit of anoptical reader clocks out (or “reads”) electrical signals correspondingto less than all of the 2D image sensor's pixels, and captures imagedata corresponding to the pixel locations into memory.

Partial frames of image data which may be clocked out and captured by anoptical reader control circuit during a partial frame capture mode areillustrated in FIGS. 4 a-4 g in which valid zones 212 represent frameimage data corresponding to image sensor pixel positions that areclocked out and invalid zones (indicated by the shaded regions of theviews of FIGS. 4 a-4 g) represent potential image data positionscorresponding to pixel positions that are not clocked out.

Border 210 defines the full field of view of an optical reader in thecase the reader is operated in a full frame captured mode while symbols216-1, 216-2, 216-3, 216-4, 216-6 and 216-7 are symbols entirely withinthe full field of view of an optical reader defined by border 10 but areonly partially within certain valid zones shown. Valid zones 212-1,212-3, 212-7, 212-8, 212-9, 212-10, and 212-13 are valid zones of imagedata that partially contain representations of a decodable symbol whilevalid zones 212-11 and 212-12 are valid zones of image data capturedduring a partial frame capture mode which contain representations of anentire decodable symbol.

In the examples illustrated with reference to FIGS. 4 a-4 e an opticalreader operating in a partial frame clock out mode clocks out electricalsignals corresponding to linear patterns of pixels. It is useful tocause a reader to clock out electrical signals corresponding to linearpatterns as shown in FIGS. 4 a-4 d when a reader will be used to decodemainly 1D linear bar code symbols.

In the examples illustrated with reference to FIGS. 4 f and 4 g anoptical reader operating in a partial frame clock out mode clocks outelectrical signals corresponding to non-linear groupings of pixels. Itis useful to cause a reader to clock out electrical signalscorresponding to pixel groupings as shown in FIGS. 4 f and 4 g when areader will be used to decode symbols which are expected to be within acertain position in an image sensor's field of view.

A reader may be configured so that the reader automatically switches outof partial frame capture mode on the sensing of a certain condition. Forexample a reader according to the invention may be made to switch out ofpartial frame capture operating mode and into a full frame capture modeon the sensing that a 2D symbol is partially represented in the partialframe of image data, or on the condition that processing of the partialframe of image data fails to result in image data being decoded.

An optical reading system in which the invention may be employed isdescribed with reference to the block diagram of FIG. 5 a.

Optical reader 110 includes an illumination assembly 120 forilluminating a target object T, such as a 1D or 2D bar code symbol, andan imaging assembly 130 for receiving an image of object T andgenerating an electrical output signal indicative of the data opticallyencoded therein. Illumination assembly 120 may, for example, include anillumination source assembly 122, together with an illuminating opticsassembly 124, such as one or more lenses, diffusers, wedges, reflectorsor a combination of such elements, for directing light from light source122 in the direction of a target object T. Illumination assembly 120 maycomprise, for example, laser or light emitting diodes (LEDs) such aswhite LEDs or red LEDs. Illumination assembly 120 may include targetillumination and optics for projecting an aiming pattern 127 on targetT. Illumination assembly 120 may be eliminated if ambient light levelsare certain to be high enough to allow high quality images of object Tto be taken. Imaging assembly 130 may include an image sensor 132, suchas a 1D or 2D CCD, CMOS, NMOS, PMOS, CID OR CMD solid state imagesensor, together with an imaging optics assembly 134 for receiving andfocusing an image of object T onto image sensor 132. The array-basedimaging assembly shown in FIG. 5 a may be replaced by a laser arraybased imaging assembly comprising multiple laser sources, a scanningmechanism, emit and receive optics, at least one photodetector andaccompanying signal processing circuitry.

The partial frame clock out mode is readily implemented utilizing animage sensor which can be commanded to clock out partial frames of imagedata or which is configured with pixels that can be individuallyaddressed. Using CMOS fabrication techniques, image sensors are readilymade so that electrical signals corresponding to certain pixels of asensor can be selectively clocked out without clocking out electricalsignals corresponding to remaining pixels of the sensor. CMOS imagesensors are available from such manufacturers as Symagery, Pixel Cam,Omni Vision, Sharp, National Semiconductor, Toshiba, Hewlett-Packard andMitsubishi. A partial frame clock out mode can also be carried out byselectively activating a frame discharge signal during the course ofclocking out a frame of image data from a CCD image sensor, as isexplained in concurrently filed U.S. patent application Ser. No.09/766,922, entitled “Optical Reader Having Reduced ParameterDetermination Delay,” incorporated previously herein by reference.

Optical reader 110 of FIG. 5 a also includes programmable controlcircuit 140 which preferably comprises an integrated circuitmicroprocessor 142 and an application specific integrated circuit (ASIC144). The function of ASIC 144 could also be provided by fieldprogrammable gate array (FPGA). Processor 142 and ASIC 144 are bothprogrammable control devices which are able to receive, output, andprocess data in accordance with a stored program stored in memory unit145 which may comprise such memory elements as a read/write randomaccess memory or RAM 146 and an erasable read only memory or EROM 147.RAM 146 typically includes at least one volatile memory device but mayinclude one or more long term non-volatile memory devices. Processor 142and ASIC 144 are also both connected to a common bus 148 through whichprogram data and working data, including address data, may be receivedand transmitted in either direction to any circuitry that is alsoconnected thereto. Processor 142 and ASIC 144 differ from one another,however, in how they are made and how they are used.

More particularly, processor 142 is preferably a general purpose,off-the-shelf VLSI integrated circuit microprocessor which has overallcontrol of the circuitry of FIG. 5 a, but which devotes most of its timeto decoding image data stored in RAM 146 in accordance with program datastored in EROM 147. Processor 144, on the other hand, is preferably aspecial purpose VLSI integrated circuit, such as a programmable logic orgate array, which is programmed to devote its time to functions otherthan decoding image data and, thereby, relieve processor 142 from theburden of performing these functions.

The actual division of labor between processors 142 and 144 willnaturally depend on the type of off-the-shelf microprocessors that areavailable, the type of image sensor which is used, the rate at whichimage data is output by imaging assembly 130, etc. There is nothing inprinciple, however, that requires that any particular division of laborbe made between processors 142 and 144, or even that such a division bemade at all. This is because special purpose processor 144 may beeliminated entirely if general purpose processor 142 is fast enough andpowerful enough to perform all of the functions contemplated by thepresent invention. It will, therefore, be understood that neither thenumber of processors used, nor the division of labor there between, isof any fundamental significance for purposes of the present invention.

With processor architectures of the type shown in FIG. 5 a, a typicaldivision of labor between processors 142 and 144 will be as follows.Processor 142 is preferably devoted primarily to such tasks as decodingimage data, once such data has been stored in RAM 146, recognizingcharacters represented in stored image data according to an opticalcharacter recognition (OCR) scheme, handling menuing options andreprogramming functions, processing commands and data received fromcontrol/data input unit 139 which may comprise such elements as trigger174 and keyboard 178 and providing overall system level coordination.

Processor 144 is preferably devoted primarily to controlling the imageacquisition process, the A/D conversion process and the storage of imagedata, including the ability to access memories 146 and 147 via a DMAchannel. Processor 144 may also perform many timing and communicationoperations. Processor 144 may, for example, control the illumination ofLEDs 122, the timing of image sensor 132 and an analog-to-digital (A/D)converter 136, the transmission and reception of data to and from aprocessor external to reader 110, through an RS-232, a network such asan Ethernet, a serial bus such as USB, a wireless communication link (orother) compatible I/O interface 137. Processor 144 may also control theoutputting of user perceptible data via an output device 138, such as abeeper, a good read LED and/or a display monitor which may be providedby a liquid crystal display such as display 182. Control of output,display and I/O functions may also be shared between processors 142 and144, as suggested by bus driver I/O and output/display devices 137′ and138′ or may be duplicated, as suggested by microprocessor serial I/Oports 142A and 142B and I/O and display devices 137′ and 138′. Asexplained earlier, the specifics of this division of labor is of nosignificance to the present invention.

Some or all of the above optical and electronic components may beincorporated in an imaging module as are described in commonly assignedU.S. patent application Ser. No. 09/411,936, incorporated herein byreference.

FIGS. 5 b-5 g show examples of types of housings in which the presentinvention may be incorporated. FIGS. 5 b-5 g show 1D/2D optical readers110-1, 110-2 and 110-3. Housing 112 of each of the optical readers 110-1through 110-3 is adapted to be graspable by a human hand and hasincorporated therein at least one trigger switch 174 for activatingimage capture and decoding and/or image capture and characterrecognition operations. Readers 110-1 and 110-2 include hard-wiredcommunication links 179 for communication with external devices such asother data collection devices or a host processor, while reader 110-3includes an antenna 180 for providing wireless communication device or ahost processor.

In addition to the above elements, readers 110-2 and 110-3 each includea display 182 for displaying information to a user and a keyboard 178for enabling a user to input commands and data into the reader. Controlcircuit 140 may cause a graphical user interface (GUI) to be displayedon display 182. A pointer on the GUI may be moved by an actuator oractuators protruding from housing 112.

Any one of the readers described with reference to FIGS. 5 b-5 g may bemounted in a stationary position as is illustrated in FIG. 5 h showing ageneric optical reader 110 docked in a scan stand 190. Scan stand 190adapts portable optical reader 110 for presentation mode scanning. In apresentation mode, reader 110 is held in a stationary position and anindicia bearing article is moved across the field of view of reader 110.

As will become clear from the ensuing description, the invention neednot be incorporated in a portable optical reader. The invention may alsobe incorporated, for example, in association with a control circuit forcontrolling a non-portable fixed mount imaging assembly that capturesimage data representing image information formed on articles transportedby an assembly line, or manually transported across a checkout counterat a retail point-of-sale location. Further, in portable embodiments ofthe invention, the reader need not be hand held. The reader may be partor wholly hand worn, finger worn, waist worn or head worn for example.

Referring again to particular aspects of the invention, control circuit140 in the example of FIG. 4 a executes a partial frame capture mode inorder to clock out and capture pixel data illustrated by valid zone212-1. Reading the pixel values of valid zone 212-1 is effective todecode 1D symbol 216-1 in the reader's full field of view. Given thatclocking out and capturing image data of valid zone 212-1 consumes lesstime than clocking out and capturing a full frame of image data, it isseen that execution of a partial frame capture mode decreases the decodetime of the reader. In prior art 2D optical readers, electrical signalscorresponding to full frame 210 are clocked out in order to decode asingle 1D symbol 216-1. The pixels of valid zone 212-1 may comprise asingle row of pixels (a scan line) or a plurality of rows.

In the example of FIG. 4 b, of control circuit 140 executes a partialframe capture mode in order to capture data defining valid zones 212-2,212-3 and 212-4 of a full frame of image data corresponding to a fullfield of view of a 2D image sensor. Valid zones 212-2, 212-3 and 212-4are line patterns of image data at various angular orientations. Readingof pixels of line valid zones arranged at various angular orientationsis effective to decode a 1D symbol which may be located at an obliqueangle in a field of view. It is seen that reading of pixels of linevalid zone 212-3 will result in the successful decoding of 1D bar codesymbol 216-2. Zones 212-2, 212-3 and 212-4 may be one or more pixelswide.

In the example of FIG. 4 c, control circuit 140 executes a partial framecapture mode in order to clock out and capture image data defining validzones 212-5 through 212-9. Valid zones 212-5 to 212-9 form a pluralityof horizontal parallel lines. The pattern of valid zones shown in FIG. 4c clocked out and captured in a partial frame capture mode is effectivefor decoding substantially horizontally oriented 1D symbols which are atan unknown height in a full field of view. It is seen that the readingof image data of valid zone 212-8 will not result in the decoding ofsymbol 216-3 because symbol 216-3 is not a 1D symbol. Nevertheless,because valid zone 212-8 intersects symbol bullseye 216-6, reading ofimage data of valid zone 212-8 may be effective to determine that a 2Dsymbol is likely present in the full field of view of image sensor 132.In one aspect of the invention, reader 110 may be configured to switchout of a partial frame capture mode and into a full frame capture modewhen reading of image data captured in the partial frame capture modereveals that a 2D symbol is likely to be represented in the image datacorresponding to the image sensor's full field of view.

The states of operation of reader 110 operating in accordance with theinvention are normally selected by actuating appropriate buttons ofkeyboard 178, or control of a GUI, or by the reading of menuing symbols,as are explained in commonly assigned U.S. Pat. No. 5,929,418incorporated herein by reference.

It should be apparent that several operating states of the invention arepossible. In a first operating state, reader 110 is made to operate onlyin a partial frame capture mode until the time the first operating stateis deactivated.

In a second operating state, as is alluded to in the example of FIG. 4c, the reader operates in a partial frame capture mode until the timethat reading of image data captured in the partial frame capture modereveals that a 2D symbol is likely to be included in the full framefield of view of image sensor 132. When reading of the partial frame ofimage data reveals that a 2D symbol is likely to be included in a fullframe field of view, control circuit 140 captures at least one fullframe of image data from sensor 132 and attempts to decode for the 2Dsymbol determined likely to be represented in the full frame of imagedata. A reader operating in the second operating state may also be madeto switch to a full frame operating mode on the condition that a symbolis not successfully decoded during operation of the reader in thepartial frame operating mode.

A third operating state of a reader operating in accordance with theinvention is described with reference to FIGS. 4 d and 4 e. Operating inaccordance with a third operating state, a reader operates in a partialframe capture mode to clock out and capture image data of valid zone212-10 which corresponds to a predetermined pattern and position infield of view 210. It is seen that reading of image data of zone 212-10will not be effective to decode symbol 216-4 because symbol 216-4 is ofa type of 2D symbol known as a stacked linear bar code. Control circuit140 may nevertheless detect that symbol is a 2D symbol given that validzone 212-10 intersects a finder pattern 216 f of symbol 216-4.

Sensing that a 2D symbol is likely present in the field of view whenreading the partial frame image data corresponding to valid zone 212-10,the reader operating in the third operating state then continues tooperate in a partial frame mode to clock out and capture image data thatdefines a second valid zone 212-11 of pixel positions as seen in FIG. 4e. The second valid zone 212-11 is not of a predetermined size andposition, but rather is of an adaptive position whose position, andpossibly size, orientation and shape depends on the result of thereading of the image data corresponding to the first valid zone 212-10.Specifically, the second valid zone 212-11 is normally at least of asize and position that is likely to encompass the symbol 216-5 detectedto be present when reading of the image data of first valid zone 212-10(labeled 216-4 in FIG. 4 d). It is seen that the third operating stateis likely to be operative to further reduce the clocking out and captureof irrelevant image data, and therefore is likely to further increasedecoding speed. In the third operating state, additional adaptiveposition valid zones may be clocked out and captured if the reading ofimage data of first adaptive valid zone 212-11 does not result in asymbol being decoded.

In the example of FIGS. 4 f and 41 g valid zones 212-12 and 212-13correspond to nonlinear groupings of pixels. Capturing of the valid zonepatterns 212-12 and 212-13 of FIGS. 4 f and 4 g is particularly usefulfor decoding symbol image data in the case that a symbol is likely to beat a certain position in relation to an image sensor's full frame fieldof view such as in the center of an image sensor's field of view asshown in FIG. 4 f.

In the example of FIG. 4 f control circuit 140 can successfully decodesymbol 216-6 because symbol 216-6 is located entirely within valid zone212-12.

In the example of FIG. 4 g, control circuit 140 cannot decode symbol216-7 if operating in the first operating state since symbol 216-7 is a2D symbol and is not entirely located within valid zone 212-13. Ifoperating in the second operating state, then a reader capturing imagedata within valid zone 212-13 may successfully decode symbol 216-7 byreading the image data of zone 212-13 to determine that a 2D symbol ispresent, switching operation to a full frame capture mode to capture afull frame 210 of image data, and processing the full frame of imagedata to decode symbol 216-7. A reader operating in the third operatingstate described hereinabove may decode symbol 216-7, in the example ofFIG. 4 g, by reading image data within valid zone 212-13, capturingimage data within an adaptively defined valid zone (not shown) ofsufficient size and position to encompass symbol 216-7, and thenprocessing the image data within the adaptively defined valid zone todecode symbol 216-7.

A bar code reading device having an image sensor including a pluralityof pixels can be operated to capture a parameter determination frame ofimage data, wherein the parameter determination frame of image dataincludes image data corresponding to light incident at less than all ofthe pixels of the image sensor. A bar code reading device can also beoperated in an image capture operating mode in which a partial frame ofimage data is captured, wherein the partial frame of image data includesimage data corresponding to light incident at less all of the pixels ofthe image sensor, and wherein image data of the partial frame can beprocessed in order to attempt to decode a bar code symbol.

According to its major aspects and broadly stated, the present inventionis a method for controlling an optical reader to reduce the reader'sparameter determination delay. According to the invention, an imagesensor is adapted to clock out image data from an image sensor accordingto two modes of operation, a “low resolution” clock out mode ofoperation and a “normal resolution” clock out mode of operation.

In a low resolution mode, some pixels of the reader's image sensor pixelarray are clocked out at a normal clock out speed sufficient to developelectrical signals that accurately represent the intensity of lightincident on the pixel array, while other pixels of the array are eithernot clocked out or are clocked out at a higher clock out rate which isinsufficient to allow development of electrical signals that accuratelyrepresent the intensity of light at the respective pixels but whichnevertheless, result in an increase in the overall frame clock out rateof the frame of image data. In a normal resolution mode of operation theimage sensor is caused to clock out electrical signals corresponding toeach pixel of the array at a constant “normal mode” speed which is aspeed sufficient to ensure that the electrical signal corresponding toeach pixel accurately represents the intensity of light incident on thepixel.

An optical reader according to the invention operates an image sensor ina low resolution mode of operation in order to clock out and capture aparameter-determining frame of image data at high speed, reads pixeldata from the parameter determination frame to determine an operationparameter based on actual illumination conditions, then utilizes theoperation parameter in operating an image sensor according to highresolution mode in the clocking out of a succeeding frame of image datathat is captured and subjected to comprehensive image data processingwhich may include image data searching, decoding, and/or recognitionprocessing. Clocking out some of the pixels of an array at high speedduring execution of the low resolution mode significantly decreases thereader's parameter determination delay.

These parameters determined by reading pixel values from a lowresolution parameter determination frame of image data according to theinvention may include an exposure time parameter, an amplificationparameter for controlling amplification of an electrical signal prior toits analog to digital conversion, an illumination level parameter(intensity or period of illumination), a dark or light level adjustmentparameter and an analog-to-digital converter reference voltage parameterfor adjusting the high and/or low reference voltages of the reader'sanalog to digital converter.

In the present invention, an optical reader image sensor is adapted toclock out image data from an image sensor according to “low resolution”mode of operation in order to reduce a parameter determination delay ofthe reader. In a low resolution mode, some pixels of the readers imagesensor array are clock out at normal clock out speed sufficient todevelop electrical signals accurately reflecting the intensity of lightat the respective pixel positions, while other pixels of the array areeither not clocked out or are clocked out at a higher clock out ratewhich may be insufficient to allow development of electrical signalsthat accurately represent light incident on the image sensor's sensorarray but which nevertheless, results in a reduction of the overallframe clock out rate of the frame of image data. An optical readeraccording to the invention operates in a low resolution frame clock outmode to capture a low resolution parameter determining frame of imagedata at high speed, reads pixel data from the parameter determinationframe to determine an operation parameter based on actual illuminationconditions, then utilizes the operation parameter in operating anoptical reader.

[Beginning of section excerpted from U.S. patent application Ser. No.09/766,806].

The invention is a method for configuring an optical reader having a 2Dimage sensor so the reader captures and processes image data at higherspeeds.

According to the invention, a control circuit of an optical readerequipped with a 2D image sensor is configured to operate in a partialframe operating mode. In a partial frame operating mode, the controlcircuit clocks out and captures less than a full frame of image data andprocesses that image data. The control circuit may process the imagedata of the partial frame, for example, by reading the image data frommemory and outputting the image data to an output location such as adisplay device or a processor system in communication with the reader,by reading and attempting to decode decodable symbols which may berecorded in the partial frame, or by reading and performing opticalcharacter recognition on characters represented in the partial frame ofimage data.

In one embodiment, the partial frame operating mode is employed to clockout and capture image data corresponding to at least one linear patternsufficient so that a 1D symbol in the field of view of the image sensormay be decoded without clocking out and capturing an entire frame ofimage data. The partial frame of image data that is clocked out from theimage sensor during the partial frame capture operating mode may be, forexample, a row of pixels at or near the center of the image sensor or alimited number of lines of image data corresponding to pixel locationsof the image sensor, possibly at varying angular orientations. Thecontrol circuit may be configured so that if the control circuit cannotdecode a 1D symbol during the course of operating in the partial framecapture mode, or detects that a 2D symbol is represented in the capturedimage data, the control circuit switches operation to a full framecapture mode.

In another embodiment, the partial frame operating mode is employed toclock out and capture pixel values corresponding to a grouping of pixelsat or near a center of an image sensor other than a linear pattern ofpixels. This embodiment may be advantageously employed in cases wheredecodable symbols are expected to be concentrated proximate a center ofan image sensor's field of view. A control circuit may be configured sothat if the control circuit cannot decode a symbol represented in thepartial frame, or determines that a symbol is represented partially orentirely outside the image data of the partial frame, the controlcircuit automatically switches operation to a full frame image capturemode.

The invention is an optical reader having a 2D image sensor that isconfigured to operate in a partial frame capture mode. In a partialframe operating mode, the reader clocks out and captures at least onepartial frame of image data having image data corresponding to less thanall of the pixels of an image sensor pixel array. In one embodiment, thereader operating in a partial frame operating mode captures image datacorresponding to a linear pattern of pixels of the image sensor, readsthe image data, attempts to decode for a decodable 1D symbol which maybe represented in the image data, and captures a full frame of imagedata if the image data reading reveals a 2D symbol is likely to bepresent in a full field of view of the 2D image sensor.

[End of section excerpted from U.S. patent application Ser. No.09/766,806].

While the present invention has been explained with reference to thestructure disclosed herein, it is not confined to the details set forthand this invention is intended to cover any modifications and changes asmay come within the scope of the following claims.

1. An apparatus for use in reading a bar code symbol, wherein theapparatus comprises in combination: an imaging assembly; a handgraspable housing; wherein the imaging assembly comprises an imagesensor having a plurality of pixels and optics focusing an image ontothe image sensor; wherein the apparatus is operable in a plurality ofuser selectable operating states; wherein the apparatus in one of theplurality of user selectable operating states is operable to capture arelatively smaller sized frame of image data and responsively to aprocessing of the relatively smaller sized frame of image data captureone or more relatively larger sized frames of image data for use inattempting to decode the bar code symbol, the one or more relativelylarger sized frames of image data having image data corresponding to apredetermined set of pixels of said image sensor and representing alarger portion of the bar code symbol than image data of the relativelysmaller sized frame of image data; wherein the apparatus in another oneof the plurality of user selectable states is operable to capture afirst frame of image data having image data corresponding to a first setof pixels of the image sensor and responsively to a processing of thefirst frame of image data capture a second frame of image data havingimage data corresponding to a second set of pixels of the image sensorfor use in attempting to decode the bar code symbol, wherein the secondset of pixels is different from the first set of pixels and wherein thepixels of the second set of pixels are adaptively determinedresponsively to a processing of the first frame of image data.
 2. Theapparatus of claim 1, wherein said apparatus is operable to capture saidsecond relatively sized larger frame conditionally on the condition thatthe processing of the relatively smaller sized frame does not result ina successful decoding of the bar code symbol.
 3. The apparatus of claim1, wherein the image sensor is a CMOS image sensor.
 4. The apparatus ofclaim 1, wherein the relatively larger sized frame of image data is afull frame of image data.
 5. The apparatus of claim 1, wherein theapparatus includes an illumination assembly.
 6. The apparatus of claim1, wherein said illumination assembly includes a laser, and wherein saidillumination assembly is adapted to project an aiming pattern.
 7. Theapparatus of claim 1, wherein the apparatus includes an illuminationassembly and wherein said illumination assembly includes a white LED. 8.The apparatus of claim 1, wherein the apparatus includes an illuminationassembly and wherein said illumination assembly includes a red LED. 9.The apparatus of claim 1, wherein the apparatus is operative to attemptto decode a 1D bar code symbol.
 10. The apparatus of claim 1, whereinthe apparatus is operative to attempt to decode a 2D bar code symbol.